Videos: Fix genre url being unusable (#4717)

Closes issue 4700

spec/invidious/videos/regular_videos_extract_spec.cr

@@ -67,7 +67,7 @@ Spectator.describe "parse_video_info" do
     # Video metadata
 
     expect(info["genre"].as_s).to eq("Entertainment")
-    expect(info["genreUcid"].as_s).to be_empty
+    expect(info["genreUcid"].as_s?).to be_nil
     expect(info["license"].as_s).to be_empty
 
     # Author infos
@@ -151,7 +151,7 @@ Spectator.describe "parse_video_info" do
     # Video metadata
 
     expect(info["genre"].as_s).to eq("Music")
-    expect(info["genreUcid"].as_s).to be_empty
+    expect(info["genreUcid"].as_s?).to be_nil
     expect(info["license"].as_s).to be_empty
 
     # Author infos

spec/invidious/videos/scheduled_live_extract_spec.cr

@@ -94,7 +94,7 @@ Spectator.describe "parse_video_info" do
     # Video metadata
 
     expect(info["genre"].as_s).to eq("Entertainment")
-    expect(info["genreUcid"].as_s).to be_empty
+    expect(info["genreUcid"].as_s?).to be_nil
     expect(info["license"].as_s).to be_empty
 
     # Author infos

src/invidious/videos.cr

@@ -250,7 +250,7 @@ struct Video
   end
 
   def genre_url : String?
-    info["genreUcid"]? ? "/channel/#{info["genreUcid"]}" : nil
+    info["genreUcid"].try &.as_s? ? "/channel/#{info["genreUcid"]}" : nil
   end
 
   def is_vr : Bool?

src/invidious/videos/parser.cr

@@ -424,7 +424,7 @@ def parse_video_info(video_id : String, player_response : Hash(String, JSON::Any
     "shortDescription" => JSON::Any.new(short_description.try &.as_s || nil),
     # Video metadata
     "genre"     => JSON::Any.new(genre.try &.as_s || ""),
-    "genreUcid" => JSON::Any.new(genre_ucid.try &.as_s || ""),
+    "genreUcid" => JSON::Any.new(genre_ucid.try &.as_s?),
     "license"   => JSON::Any.new(license.try &.as_s || ""),
     # Music section
     "music" => JSON.parse(music_list.to_json),